code: def layer_op(self, pred_real, pred_fake, var_scope=None):
      with tf.device("/cpu:0"):
          g_loss = self._data_loss_func["g"](
              pred_fake, **self._loss_func_params
          )
          d_fake = self._data_loss_func["d_fake"](
              pred_fake, **self._loss_func_params
          )
          d_real = self._data_loss_func["d_real"](
              pred_real, **self._loss_func_params
          )
      return g_loss, (d_fake + d_real)
  
file_path: NiftyNet/niftynet/layer/loss_gan.py
imports: from __future__ import absolute_import, print_function
  import tensorflow
  from niftynet.engine.application_factory import LossGANFactory
  from niftynet.layer.base_layer import Layer
label_desc: Use image node_id 3 for calling the LossFunction obj's underlying member method code with example usage: obj.layer_op(pred_real, pred_fake, var_scope) and returns: g_loss,  unknown